I have categories for fuel, groceries, entertainment etc. etc. I also have a vacation category. My question is, when I buy gas during the vacation should I post it to fuel or vacation category?
I usually want to simplify when on vacation and will chalk everything up to Vacation.
A follow-on issue is when to record transactions if you're not hooked into Direct Import. I typically blow off recording transactions while traveling, import them upon my return from a file, and bulk-recategorize everything to Vacation. Simple and convenient.
Recording as you go would make a lot of sense if you're relying on YNAB for spending guidance during the trip.
Regardless of when you record, Fuel/Groceries/etc. are likely to have more money than necessary, which can be moved into Vacation beforehand or to cover overspending.
I think I would post it to vacation. That way, when you look back to see your average fuel use (maybe to adjust your budget moving forward) it won't be distorted by the vacation.
If you want to include the vacation costs to the regular categories (ex: staying in an airbnb and cooking your own meals - it makes sense to include that as groceries) BUT you still want to see the total cost of your vacation, add "Aspen" to the memo of any transaction involving your trip. Then, after your trip, you can do a total accounts search for "Aspen" and see how much the total trip cost.